My iPhone 4s won't charge? - 1

I got my phone in the middle of January this year. I was charging it on my laptop and it suddenly just stopped. So i took out the usb and put it into the wall charger thing and it didn't make a difference. I know that its not the charger because it lights up then its plugged in. It got overheated only once and that was a while ago. What's wrong with my phone? What should I do?

Take it to an Apple genius bar. It is free.